Ink compositions comprising water and a water dispersible resin are known in the art. These ink compositions are also known as latex ink compositions. Droplets of these inks may be applied onto a receiving medium by jetting droplets of these inks using an inkjet printing apparatus. Generally, latex inks further comprise a colorant, such as a pigment in addition to the dispersible resin and water. Water functions as a vehicle for the other components of the ink composition. However, water may evaporate from the latex ink composition. Evaporation of water from the ink may be desired once droplets of the ink have been applied onto a receiving medium to form an image. On the other hand, evaporation of water may be undesired when the ink is still in the print head. For example, evaporation of water may result in precipitation of components of the ink composition, for example precipitation of the resin or the colorant. Precipitation of these solids may result in clogging of the nozzles, thereby decreasing the jetting performance of an inkjet printing apparatus. It is therefore desired to prevent precipitation of solids from the ink composition. It is known that the evaporation of the ink vehicle may be diminished by (partially) exchanging water for a water-soluble co-solvent. These water-soluble co-solvents may have a low volatility, such that the vehicle evaporates slower and the ink composition stays stable for a longer period of time. However, although changing the composition of the ink vehicle may slow down evaporation, the vehicle may still evaporate, resulting in clogging of the nozzle, which may lead to nozzle failure. Once the vehicle is evaporated, the solid particles of the ink composition are not stabilized anymore. Therefore, it may not be possible anymore to re-disperse the solid components of the ink composition after evaporation of the ink vehicle. Thus, precipitation of the solid particles of the ink composition may be irreversible.
Furthermore, the ink vehicle comprising the water-soluble co-solvent has to be removed after printing. Applying co-solvents having low volatility may increase the energy requirements for drying the prints, compared to inks having an essentially aqueous vehicle, and/or may necessitate the use of porous receiving media for absorbing the co-solvents. In addition, evaporation of co-solvents may result in the formation of vapors that are undesired from a health, safety and environmental point of view.
It is therefore an object of the invention to provide a latex ink composition that mitigates the above mentioned problems.